The invention relates to an examining system for the two-dimensional imaging of structures of an object on a receiver, such as a camera, by means of charged particles, such as electrons. In particular, the examined structures may be structures which are usually examined by electron-microscopy, wherein backscattering electrons, secondary electrons, transmission electrons or photoelectrons emerging from the object are observed. The invention is not intended to be limited to these types of electrons. In particular, the observation of ions emerging from the object is also contemplated.
Furthermore, the invention relates to a deflector for beams of charged particles. In particular, said deflector is suitable for use in the examining system for examining the object. However, the use of the deflector is not intended to be limited to this application. Moreover, the invention relates to a method for the operation of the deflector.
A possible field of application of the examining system is in methods for the manufacture of miniaturized devices and, here, in particular, for localizing defects of the devices during the manufacture of the same and of the masks used for this purpose, such as lithography masks. U.S. Pat. No. 5,578,821 discloses an examining system for this purpose wherein an electron beam is focused onto a point (pixel) of the object to be examined. Backscattering electrons, secondary electrons and transmission electrons emerging from the object are recorded by appropriate detectors. In this system, a deflector is used to displace the location where the focused beam impinges on the object. The respective detectors integrally receive all backscattering, secondary and transmission electrons independent of the displacement of the location. The detectors as such are not position-sensitive, but it is possible to obtain a position-resolved image of the structures of the object if the intensity recorded by a detector is allocated to the point determined by the deflector where the beam impinges on the object. By operation of the deflector, the beam is then successively deflected to the different locations (pixels) of the object, the measured intensities allocated to the different locations are recorded and the two-dimensional image is composed of the successively recorded intensities. This method is very time-consuming.
U.S. Pat. No. 6,097,659 discloses an examining system, wherein a two-dimensionally extended field on the object is irradiated with primary electrons and wherein secondary electrons emerging from the object are imaged on a position-sensitive detector. In contrast to the system disclosed in U.S. Pat. No. 5,578,821, this renders a sequential scanning of pixels by means of a deflector superfluous. Rather, a multiplicity of pixels can be simultaneously detected. However, if a high magnification of the image is desired, the field imaged on the detector is too small to image an object of larger two-dimensional extension at once. Therefore, a mechanical shift table is provided for the object to be displaced relative to the illuminated field, so that the detector can pick up, successively in time, a plurality of images of the object, the latter being displaced step-by-step, in order for an image of the entire object to be eventually obtained by combining the plurality of images. This, again, is very time-consuming and, moreover, requires a shift table whose mechanical precision corresponds about to the desired resolution of the image.